How do you add a fog effect or make certain things seem farther away?
There are at list 2 easy ways to accomplish that, one is while rendering, other is post-process the render. If you want to do it while rendering (will get slower render) you have to create a volumetric object, with volume absortion nodes (under material). To do on post process (will be faster) you have to activate while rendering the option "mist pass". After rendering, in the compositer, you can link the mist pass to your rendered images and set density, color, etc. https://www.youtube.com/watch?v=CxNeMMZs_sM